Minimizing energy consumption is highly desirable whenever the costs of energy can have a direct impact on the overall operating costs of a system. Very often, minimizing energy consumption also reduces carbon footprint.
There are different possible approaches for minimizing energy consumption. One approach is to use more efficient machines and method for extracting energy from an available heat source. Heat pumps systems are one example of machines following this approach when applied to heating. In these systems, heat from a first medium is captured using a refrigerant circulating in a cold side and a second medium is heated using the same refrigerant circulating in a hot side. Heat pump systems are also well known for use in refrigerators or air conditioning systems.
Still, heat pump systems can be used for freezing a liquid, for instance water, in order to purify it. When water freezes, it forms substantially pure ice crystals. Over the years, this characteristic was used for different purposes, such as the recovery of fresh water from salt water or for treating effluents from industrial processes. Examples of systems are disclosed in U.S. Pat. No. 3,098,735 issued on 23 Jul. 1963 to Clark, U.S. Pat. No. 3,137,554 issued 16 Jun. 1964 to Gilliland et al., U.S. Pat. No. 3,338,065 issued 29 Aug. 1967 to Ashley, and U.S. Pat. No. 4,199,961 issued on 29 Apr. 1980 to Carter et al., to name just a few.
Some heat pump systems were designed for extracting latent heat released when liquid water freezes in their cold side. When freezing, liquid water goes through a phase change and releases about 335 KJ of latent heat per kilogram of water. This represents about 15 times more energy than using only sensible heat from cold liquid water. As an added benefit, less water is required. However, one of the challenges of ice-generating heat pump systems is the relative complexity involved in operating them on a continuous basis. In particular, ice tends to accumulate on the cold side of the heat pump systems, thereby requiring frequent defrost cycles. This reduces the overall efficiency of these systems.
U.S. Pat. No. 4,671,077 issued on 9 Jun. 1987 to Paradis discloses a system where the latent heat from freezing water is used as a source of energy. The water can be salt water or polluted water and this water can be purified as a result of the freezing. Although the disclosed system has potential benefits in terms of energy efficiency, there are still many challenges that one would need to overcome before such system can be operated continuously with an optimum efficiency and on a large scale.
Accordingly, there is still room for many improvements in this area of technology.